Most ppl dun know about subaru boxer engine well, their piston is horizontal opposed, more balanced n low center of gravity, but bcos of that gravity will make the block bore oval over long mileage, say 100k depend how u drive n maintain it(some can go 300k well maintain), then when u overhaul the engine, only can bore bigger(stock piston have bigger size option, resleeve block too expensive but more reliable) That y u c most subaru is stroked. A 2.2 is oversize piston with 2.5 crank(normal oversize is 2.1 only), so liability is not an issue if not very high boost(over 1.5bar) for daily driven, must maintain well with full syn oil n properly warm up b4 high rev. hope this help on your choosing your ride.
Any spec up from normal STi is lighter n faster... Try to find where the car was maintain b4 n get all the info that u can get b4 decide, if no record better not risk it.
FYI.. i bought my subaru in 2.2 also, all i can say is "POWER"